Attempts to provide generalized motion simulation through the use of electromechanical or hydromechanical apparatus have heretofore been proposed. Typical examples are illustrated by U.S. Pat. Nos: 3,619,911 issued on Nov. 16, 1971 to E. G. Pancoe, 3,529,354 issued on Sept. 22, 1970 to D. D. Roberts et al., 3,304,628 issued on Feb. 21, 1967 to L. Kaplan, 3,295,224 issued on Jan. 3, 1967 to K. L. Cappel, and 3,281,962 issued on Nov. 1, 1966 to E. G. Pancoe. Observation of these prior inventions reveal two general categories or types of motion system designs. These two types are referred to, by those familiar in the art, as the synergistic and cascaded types of motion systems. The synergistic type systems as examplified in Roberts et al. U.S. Pat. No. 3,529,354 are characterized by a single movable platform, wherein pure movement of this platform and its payload in any axis of motion requires a coordinated effort from a plurality of actuators. The cascaded type motion systems as examplified by the E. G. Pancoe et al. U.S. Pat. No. 3,619,911 are characterized by multiple stages of movable platforms, gimbals, guides, or the like, wherein pure movement of the principal platform and its payload in any axis of motion requires an effort from a single actuator. In addition to the synergistic or cascaded categorization, these prior inventions can also be categorized by the number of degrees of freedom which they can provide. Some systems can provide only two or three degrees of freedom to a platform, while others can provide four, five, or even the full compliment of six degrees of freedom.
Several design goals have been common to all motion systems employed in vehicular flight simulators used to train students. The first of these goals has been that the movement provided in each axis of freedom have sufficient excursion, velocity and acceleration capability and be sufficiently controllable to reproduce, with realistic time delays, the frequencies and amplitudes of those accelerations which would be imparted to the actual vehicle flight compartment. Sufficiently controllable meaning within the tolerance of human perception.
Another goal has been that the movement provided in each axis be smooth enough to control the gradual truncation of acceleration cues and the application of subliminal position and velocity washouts. Other common objectives of motion systems have been that they be mechanically failsafe, wherein the members of the system will not mechanically interfere with one another and the movable platform will not collapse or move into a position in which it cannot return. Some of the more recent motion systems have had an objective of accommodating various visual display systems.
The major problems associated with prior motion systems have been due to their inability to control the movement of a platform and its payload within the tolerance of human perception of what is generally defined as motion noises. This perceivable motion noise is commonly referred to as "false cues", since they have no counterpart in the real vehicular flight environment. The cause of this noise can be related to the electronic control circuitry and the computer drive equations, but more often is related to structural spring reactions of the mechanical elements of the system and to the load variations on the system actuators. Many of the prior system designs assumed the movable platform and other mechanical components to be perfectly rigid. They also assumed the actuators to be unaffected by load variation throughout their range of extention and retraction. In system applications where the moving payload has been light and small in size, and where the required acceleration levels in each axis have been low, these assumptions proved to be acceptable. However, the trend in flight simulation has been to increase the weight of the movable payload due to requirements of on board instructor stations and multiwindow visual display systems. There has also been a tendency toward increased acceleleration performance requirements in all axes of motion due to the general improvements in vehicle performance over the years. These two factors have invalidated the assumptions that the structural components of a motion system act as rigid elements, and that actuator performance is unaffected by load variations. The result has been that prior motion system designs have had to suffer performance degradation to eliminate the generation of false motion cues. Either the acceleration levels had to be reduced, or electronic compensation networks or computer programmed compensation equations had to be incorporated which resulted in a lower system frequency response.
The present invention proposes a novel geometric arrangement or actuators which mechanically minimizes these system noise problems and will simplify or eliminate the need for control compensation. Structural spring problems are automatically reduced by the fact that the present invention is of the synergistic type, having only one movable platform and six linear actuators. Dynamic and static load variation problems are minimized by an appropriate arrangement of actuator attachment points and lines of action, wherein movement along or about any axis of the platform will transmit minimal or no forces and moments into other axes of motion. This novel geometric arrangement may not provide the optimal solution to all motion simulation problems, but does not claim to provide a significant improvement in motion fidelity over prior known systems.